Discovery of linkage in bacteria

Content
Sexuality and Recombination in Bacteria and Viruses
Three Methods for Transfer of Genetic Material 
Sexual conjugation in bacteria 
Culture media and mutant strains
Discovery of gene transfer
Discovery of linkage in bacteria
Donor and recipient strains
- Mechanism of chromosome transfer
- Physical structures involved in chromosome transfer
Linkage maps in bacteria
Conjugation mapping through interrupted mapping
Circular linkage map
Linkage information from transformation
Recombination after gene transfer
High resolution mapping
Linear order of genes
Replication and recombination in viruses 
Replication of bacteriophages
Lysogenic bacteria
Transduction
Recombination in viruses
Circular genetic maps in viruses


A simple two step experiment was performed by Lederberg and Tatum, using the above two strains (strain A = met-bio-thr+leu+thi+ and strain B = met+bio+thr-leu-thi-) to test whether or not the genes are organized into linkage group(s). In step one, a mixture of A and B was grown on a minimal medium supplemented with biotin so that both met+bio+thr+leu+thi+ as well as met+bio-thr+leu+thi+ could grow. They were designed as met+bio?thr+leu+thi+. In step two, the colonies grown on biotin supplemented medium were tested on minimal medium (deficient for biotin) and were classified into two categories (bio+ and bio-). Similar tests were performed with other supplements (threonine, leucine and thiamine) also and the results are presented in Table-12.1, which suggests linkage, because in the absence linkage, due to independent assortment 1 : 1 ratio between + and - strains for each supplement should be obtained.

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